Abstract

Three-dimensional bent slot waveguides are analyzed using a combined effective-index method/modified transfer-matrix method. The effective refractive index and bending loss of the guided mode can be acquired. The results closely match those calculated by the full-vectorial finite-difference method. This method also enables the calculation of field distribution, useful in estimating power confined in the narrow slot, and can handle asymmetric bent slot waveguides, bent multiple-slot waveguides, and hybrid bent slot waveguides. This approach has advantages of simplicity, versatility, and time-saving calculation, which are beneficial for the quick design of devices using bent slot waveguides.

Effective refractive index and (b) bending loss of an air-clad silicon bent single-slot waveguide (η=0.5, w=400nm, and h=250nm) as a function of the bending radius for the fundamental quasi-TE mode under various slot sizes.

(a) Schematic of a curved double-slot waveguide; (b) normalized ∣Er∣ of an air-clad silicon bent double-slot waveguide with w=400nm, h=250nm, g1=g2=50nm, R=2.5μm, and η1=η2=0.25 for the fundamental quasi-TE mode. The effective refractive index of this structure is equal to 1.55619.